Corrugated paperboard and method of making the same



March 17, 1931. v SCHQO 1,796,542

CORRUGATED PAPER BOARD AND METHOD OF MAKING THE SAME Filed 001.. 7, 1930IN V EN TOR.

, CZARf/VCZJ S0700 l I I I I p c b c D q i I I a ATTORNEYS.

Patented Mar. 17, 1931 UNITED STATES 1 .'rr.1-rr OFFICE CLARENCE J.SCHOO, 0F SPRINGFIELD, MASSACHUSETTS, ASSIGNOR T0 GENERAL FIBRE BOX 00.,OF WEST SPRINGFIELD, MASSACHUSETTS, A CORPORATION OF MASSA- GHUSETTSCORRUGATED PAPERBOARD AND METHOD OF MAKING THE SAME Application filedOctober 7, 1930. Serial No. 486,931.

In the manufacture of corrugated paper board the general procedurefollowed is to pass a Web of suitable heavy paper, which in pastpractice has generally been formed of a straw base, between heatedmeshing fluted rolls. F or the proper control of the paper the paper webis supplied to the rolls under tension and is forced into corrugatedform by the action of the alternating ridges and valleys on the tworolls. These rolls are generally held in meshing relation under a heavyspring pressure which permits the rolls to yield and thus to accommodatethemselves to irregularities in the thickness of the paper web. In orderto set the paper in its corrugated form it is generally steamed beforepassing between the rolls, and the rolls are heated to dry out themoisture and to give an ironing action which causes the paper to retainthe shape given to it by the corrugations.

While the Web thus corrugated is still supported by one of the rolls, anadhesive is applied to the crests of its corrugations on one side. Aseparate web, called a lining sheet, is applied to the adhesive coatedside of the corrugated web, being bridged across the crests of thecorrugations and imparting a truss-like rigidity to the two-plylaminated product. This material is sometimes used in its two-ply form,being known as singlefaced corrugated board but in order to make astronger product a lining sheet is usually added upon the other side,the crests of the corrugations on the second side of the corrugated webbeing previously coated with adhesive. This product is known as double.faced corrugated board.

While my invention, as will appear from the description below, has withbeneficial results been applied to the single faced prodnot, its fulladvantage is felt only with double faced board. The latter product willtherefore be considered chiefly in pointing out the diiiicultiesinherent in former methods of manufacture and overcome by the use of myinvention. The two lining sheets of the double faced board lie parallel,to each other and are adhesively secured to opposite sides of thecorrugations, giving a double trussing action which impartsgreatrigidity to the composite board. Variations in the height of thecorrugations, or failure of the corrugations to reach the height atwhich maximum rigidity is obtained, affect the strength of the productseriously. If some corrugations are lower than others, they may notreceive any adhesive or may fail to make contact with the lining sheet.If some corrugations are higher than the average, they may be crusheddown in applying the second lining sheet. fective and is easily bentalong the line of each improperly formed corrugation.

In past practice, attempts to corrugate the central web uniformly to theproper height by using a high pressure between the rolls have not beenuniformly successful. While some grades of paper, such as the relativelylow-strengthstraw paper, have been corrugated commercially, attempts tosecure equivalent corrugating efi'ect with papers of higher strengthhave met with diliiculties of considerable magnitude. Among thesedifficulties may be mentioned the weakening or actual rupture of thepaper during corrugation when a pressure was employed sufiiciently hightomake corrugations of uniformly fullv height; the failure to force thepaper all the way into the flutings of the corrugating rolls;irregularities in the height of the corrugations produced; and stickingof the paper to the rolls with a consequent tearing ofi of a portion ofthe paper fibers. It is the object of my invention to avoid thesedimculties, to improve the speed of production and the quality of theproduct, and to render possible the corrugation with substantially equalfacility of a wide variety of papers.

one important step in my improved process, I apply a very thin film of alubricant such as melted paraflin to the tops of the ridges orcorrugation on the 'corrugating rolls. As a result all of desirableresults above referred to may be secured. More particularly a-kraftpaper may be used successfully as the corrugated sheet in a high speedmachine, something which as far as I In either event, the board isdeknow has never heretofore been accomnot entirely understood by me. Itis not believed to be merely a case of reducing friction of the paper inmoving over the corrugations of the rollers because these corrugationsare of smooth and polished steel, offering very little friction andtests have demonstrated that some papers may be successfully used in myimproved method, which could not be satisfactorily used heretofore eventhough they gave every indication of being smoother and offering lessfriction than the straw paper which has in the past offered lessobjection than most other types of paper.

I am aware that paper has been coated or saturated with paratlin tofacilitate bending into predetermined shapes or to assist in theretaining of such shapes but such prior practice is not to be confusedwith my improved method.

It is important that in my improved process the paper shall not becoated to any such extent as will prevent the steam or moisture in thepaper from being rapidly driven out by the heat of the corrugatingrollers. Silicate of soda is the adhesive most commonly employed forsecuring the liners to the crowns of the corrugations of theintermediate sheet. The amount of paraffin added must also be so slightthat it does not interfere in any way with application of the adhesive,whatever its kind, or the prompt efficient and lasting action of theadhesive in connecting the sheets together along the narrow lines oftangeney of the corrugation crowns with the parallel lines to form arigid structure.

Experience has demonstrated that one pound of paraffin is all that isneeded for making at least 17,000 square feet of double faced paper fromwhich it will be seen that the film of paraffin on any portion of thesurface of the paper is so thin that it is immeasurable; can have nowaterproofing or coating effect; does not fill the interstitial spacesin the paper: does not change the appearance or feel of the product; anddoes not interfere with the aste from being re-treated for furthermanufacture into paper products.

So far as T am aware, the low percentage of paraffin which is used in myparaffin treating process and is incorporated into my improved doublefaced corrugated board would have no effect whatever in any other artwhere it has been customary to use paraffin coated or saturated paper.Furthermore such paraffin treated papers as are commonly used in otherarts have entirely too high a percentage of paraffin to permit of theirsatisfactory use in securing the results accomplished by my improvedmethod of making double faced corrugation paper.

The paraffin is advantageously applied in liquid form by means of wickshaving wiping engagement with the outer edges only of the successiveridges or corrugations of the rollers. The rollers being heated mayserve weasee to keep the paraffin melted in the supply re ceptacle or itmay be kept melted in other ways but it is important that the paraffinbe kept from solidifying in and closing the pores of the wicking. As thewicking contacts with the heated rollers, the heat of the rollers servesthis function.

The invention will now be described with particular reference to theaccompanying drawings, in which:

Fig. 1. is a diagrammatic representation of mechanism by which myimproved process may be practiced; and

Fig. 2 is a perspective detail of a fragment of corrugated board.

The web a of material to be corrugated passes over guide rolls 10 and asteaming device 11 to the surface of a corrugating roll 12. This rollhas teeth 13 meshing with similar teeth 1% on a second corrugating roll15. The roll 12 is mounted on a bracket 16 pivoted at 17 to a stationarypart of the machine and is pressed towards the roll 15 by a compressionspring 18. As the paper Web passes between the two corrugating rolls, itis forced into its final corrugated condition, and is set in thiscondition by the heat of the rolls, generally kept at over 300 F. Thisheat is generally supplied by steam circulated through the hollowinterior of the rolls. An adhesive applying roll 19 runs in contact withthe corrugated paper on roll 15 and applies a film of adhesive such assodium sili- 'ate to the high points of the corrugations. This rollreceives adhesive from a supply roll 20 dipping into a tank 21. A liningweb b is passed over a roll 22 running adjacent to the surface of roll15, and is pressed thereby into adhering contact with the corrugatedpaper. The composite web then passes an adhesive applying roll 23, whichreceives adhesive from a roll 24 and a tank 25 and applies adhesive tothe second side of the corrugated web. The second lining sheet 0 ispassed around a roll 26 and is pressed against the corrugated web bythis roll and a mating roll 27.

This arrangement of apparatus has been described rather briefly, as itis common in the art. It does, however, illustrate the environment withwhich the mechanism now to be described is combined to produce the novelresults referred to above. According to my invention the lubricant ispreferably applied to the crests only of the flutings on the corrugatingrolls, being allowed to spread over the remainder of the roll surface.This spreading takes place with considerable rapidity on account of theheat of the rolls, and I have found this method of application to haveseveral features of advantage. In the first place, the portions of theroll flutings which required the maximum lubrication are the crest andthe sides. It is the crest which ICLEIYCS the maximum frictional contactof the paper during the drawing of the paper around the roll intocorrugated form. It is the sides to which maximum pressure is appliedduring the actual corrugating, and to which the paper is most likely tostick. The bottom of the groove gives comparatively little troubleduring the corrugating operation, and requires little if anylubrication. The bottom of the roll flutings, moreover, corresponds tothe crest of the corrugation which is formed in the paper, and it is tothis point that the adhesive is subsequently applied. Any appreciablequantity of lubricant will harmfully aifect the sticking of the adhesiveto the paper, and it is thus of importanceto prevent the accumulation ofan excess of lubricant at the bottoms of the roll flutings. My preferredmanner of applying lubricant to the roll surface consists in permittingthe outer portions of the flutings to wipe against a wick saturated withthe lubricant. This has certain advantages over other methods ofapplication such for example as spraying, for in the latter case theforce of the spray would tend to cause an accumulation of lubricant atthe bottom of the flutings with a minimum at the top and sides, thereverse of the condition desired.

Referring now to the mechanical details of the apparatus which forms thepreferred embodiment of my invention, a tube 30, closed at its ends, islocated adjacent the roll 12. Flanges 31 are secured in parallelrelation along this roll, leaving between them a space communicatingwith the interior of the tube. A wick 32 fills this space and is subjectto compression to any de ree desired by one or more adjusting screws.%3y tightening the screws the wick will be compressed and the amount oflubricant delivered from the interior of the tube 30 will be lessened.The tube is positioned close to the roll 13, conveniently between it andthe steaming device 11, so thatwhen paraflin is used as a lubricant thenormal heat of the surrounding parts will be sufiicient to preserve theparafiin in molten condition without the use of special means forheating the tube. The wick 32 is positioned so that it drags upon theperiphery of the corrugated roll 12, spreading a thin layer of thelubricant upon the crest of the flutings. As the tube is limited in sizeon account of its position and is for the same reason rather difficultto fill with lubricant, it is preferably kept filled from an externalsource. For this purpose it is con- 'nected by a flexible conduit 34 toa steam jacketed tank 35 which may be positioned wherever convenient.

Above the second corrugating roll 15 is a funnel-shaped trough 36 havinga wick 37 clamped between its lower edges by one or more adjustingscrews 38. This trou h is also so located relative to the normally eatedmachine parts that in practice para will be kept melted in it due to theheat of the corrugating rolls, and a separate steam jacket will beunnecessary, The wick 37 drags over the crests of the flutings on theroll 15 in the same manner as has been described with relation to thewick 32.

It will be noted that the wick 32 applies its lubricant to the crests ofthe flutings on roll 13 prior to the contact of the web a with it. Theweb travels at a speed higher than the surface speed of the roll, onaccount of the surplus material required for the formation of thecorrugations. The lubrication greatly decreases the frictionalresistance necessary to be overcome in drawing to the corrugating pointthe amount of paper required. It also facilitates the actual corrugatingoperation and prevents stickin of the paper to the roll. The valleys ofthe utings on roll 12, which preferably receive the lubricant onlythrough spreading and not directly from the wick, and which thereforereceive the minimum amount, correspond to the crests of the corrugationswhich later contact with the adhesive-applying roll 19 and with thelining sheet b. While the total amount of lubricant appliedis'preferably very small (it may be on the order of onethousandth of anounce of paraflin per square foot of paper), this gives added insurancethat on the crests of the corrugations there will not be a quantity oflubricant sufiicient to prevent the later applied adhesive fromadhering. Similar remarks of course apply to the wick 37.

Claims:

1. Double faced corrugated paper board comprising a centralcorrugatedweb'and a pair of lining webs, one adhesively secured to thecrests of the corrugations on each side of the central web, said centralweb carrying paraffin in suificient quantity to permit its uniformcorrugation to full height without undue strain but insuficient inquantity to affect the sticking theretoof the adhesive joining it to thelining webs, to produce an appreciable waterproofing effect in thecentral web, or to produce any commercially perceptible change in thenatural properties of the paper out of which the central corrugated webis formed, the paraflinbeing carried by the central web in maximumamount on the inside of the crests of the corrugations and in minimumamount on the outside of said crests.

2. Double faced corrugated paper board comprising a central corrugatedweb and a pair of lining Webs, one adhesively secured to the crests ofthe corrugations on each side of the central web, said central webcarrying parafiin distributed thereon in a concentration of the order ofone thousandth of an ounce per square foot, the paratfin being presenton the inside surfaces of the crests of the corrugations of the centralweb in sufii- 4 messes cient quantity to insure uniform full corrugationof the Web to full height Without undue strain and present on theoutside surfaces of the crests of said corrugations in insufiicientquantity to prevent sticking E thereto of the adhesive joining it to thelining Webs.

3. Double faced corrugated paper board comprising a central corrugatedWeb and a lining Web adhesively secured to the crests w of thecorrugations on each side of the-central web, said central web beingcorrugated uniformly and fully and carrying a lubricant suiiicient inquantity to permit its uniform corrugation to full height Without undue15 strain but insufiicient in quantity to produce any commerciallyperceptible effect upon the natural properties of the paper or upon thesticking thereto of the adhesive joining it to the lining Webs.

4. A method of corrugating paper which comprises subjecting the paper tocorrugating pressure between preformed surfaces in the presence of anintervening lubricant suf- F ficient in amount to cause the paper to befully and uniformly corrugated but insufiicient to be commerciallyperceptible in. the corrugated product.

5. A method of corrugating paper which comprises subjecting the paper tocorrugatimp pressiuie between heated preformed surfaces in. the presenceoi? an intervening film of molten paraiiin. sui'licient in amount tocause the paper to be fully and uniiorrnly 35 out insui' cient to hecommercially ceptioie in the corrugated prodmzt, said pciailin. neing o"inuted in a concentration of the order or one thousandth oi en ounceper square foot or the pap-er.

ii. method of corrugating paper which. comprises steaming bhe paper,subjecting the moist paper to con n aring pressure between. ueforincd sufaces in the presence of vening film. of molten paraiiin sufiicient inamount to cause the paper to be fully and uniformly corrugated butsuiiicient to be commercially perceptible in the corrugated product,

'7. method oi? corriigating paper by heat 50 ano pressure betweenpreformed surfaces 1 "\in lubricant to the oi the surface pressing thepaper xetner the surfaces siinultancwsly subjecting it to the action eiiheat. applying an adhesive to the crests the corrugations in the paper,so that the adhesive contacts with portions of the paper aiiected onlyby such lubricant as has migrated over the tinted surfaces and presseoinn lining; sheets upon. the adhesive coated corrugations.

in t LllnOIlj whcreoi i have attired my signature.

CE J. SGHQG C

